Borderless Contacts for Semiconductor Devices

ABSTRACT

In one exemplary embodiment of the invention, a method (e.g., to fabricate a semiconductor device having a borderless contact) including: forming a first gate structure on a substrate; depositing an interlevel dielectric over the first gate structure; planarizing the interlevel dielectric to expose a top surface of the first gate structure; removing at least a portion of the first gate structure; forming a second gate structure in place of the first gate structure; forming a contact area for the borderless contact by removing a portion of the interlevel dielectric; and forming the borderless contact by filling the contact area with a metal-containing material.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation patent application of co-pending application Ser.No. 12/617,084 filed Nov. 12, 2009, which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

The exemplary embodiments of this invention relate generally tosemiconductor structures and, more specifically, relate to borderlesscontacts for semiconductor devices and the formation thereof.

BACKGROUND

The following abbreviations are utilized herein:

CA contact areaCD critical dimensionCMOS complementary metal-oxide semiconductorCVD chemical vapor depositionDRAM dynamic random access memoryFET field effect transistorFUSI fully silicidedLPCVD low-pressure CVDMOSFET metal oxide semiconductor field effect transistorPECVD plasma-enhanced CVDRIE reactive ion etchSTI shallow trench isolation

Semiconductors and integrated circuit chips have become ubiquitouswithin many products due to their continually decreasing cost and size.In the microelectronics industry as well as in other industriesinvolving construction of microscopic structures (e.g., micromachines,magnetoresistive heads, etc.) there is a continued desire to reduce thesize of structural features and microelectronic devices and/or toprovide a greater amount of circuitry for a given chip size.Miniaturization in general allows for increased performance (moreprocessing per clock cycle and less heat generated) at lower powerlevels and lower cost. Present technology is at or approaching atomiclevel scaling of certain micro-devices such as logic gates, FETs andcapacitors, for example. Circuit chips with hundreds of millions of suchdevices are not uncommon. Further size reductions appear to beapproaching the physical limit of trace lines and micro-devices that areembedded upon and within their semiconductor substrates. The presentinvention is directed to such micro-sized devices.

Basically, a FET is a transistor having a source, a gate, and a drain.The action of the FET depends on the flow of majority carriers along achannel between the source and drain that runs past the gate. Currentthrough the channel, which is between the source and drain, iscontrolled by the transverse electric field under the gate. More thanone gate (multi-gate) can be used to more effectively control thechannel. The length of the gate determines how fast the FET switches,and can be about the same as the length of the channel (i.e., thedistance between the source and drain). Multi-gate FETs are consideredto be promising candidates to scale CMOS FET technology down to thesub-22 nm regime.

The size of FETs has been successfully reduced through the use of one ormore fin-shaped channels. A FET employing such a channel structure maybe referred to as a FinFET. Previously, CMOS devices were substantiallyplanar along the surface of the semiconductor substrate, the exceptionbeing the FET gate that was disposed over the top of the channel. Finsbreak from this paradigm by using a vertical channel structure in orderto maximize the surface area of the channel that is exposed to the gate.The gate controls the channel more strongly because it extends over morethan one side (surface) of the channel. For example, the gate canenclose three surfaces of the three-dimensional channel, rather thanbeing disposed only across the top surface of the traditional planarchannel.

As the CDs of CMOS devices are being aggressively scaled, formingcontacts on those small devices is becoming more and more difficult doto the tight overlay tolerance. Borderless contacts and techniquesrelating thereto help reduce the amount of space required for contacts,and enable production of smaller devices having a tighter pitch.Reference in regard to borderless contacts may be made to:commonly-assigned U.S. Pat. No. 4,944,682 to Cronin et al.,commonly-assigned U.S. Pat. No. 4,966,870 to Barber et al. andcommonly-assigned U.S. Pat. No. 5,759,867 to Armacost et al. Borderlesscontacts have been used in devices with tight pitch, particularly inmemory products (e.g., DRAM). Reference in this regard is made tocommonly assigned U.S. Pat. No. 6,709,926 to Chidambarrao et al.Borderless contacts are usually formed with a gate stack including agate dielectric, a gate conductor and an insulating cap. The gateconductor usually comprises polycrystalline silicon (also referred toherein as “poly” or “polysilicon”). In some cases, metal or metalsilicide is added on top of the poly in order to lower gate resistance.Reference in this regard may be made to U.S. Pat. No. 5,966,597 toWright and U.S. Pat. No. 6,236,094 to Wright.

High-k/metal or FUSI gates have been proposed and projected to fulfillfuture CMOS scaling. A MOSFET with a metal gate can be formed by eitherso-called “gate-first” techniques or “gate-last” techniques. In agate-first technique, metal gates are deposited and patterned duringgate formation. A poly cap layer on top of the metal layer is usuallyprovided to achieve proper and stable workfunction of the gate stack. Itis often further desired to form a silicide on top of the poly cap layerafter source/drain formation in order to lower gate resistance. In agate-last technique, a dummy gate is first formed in order to facilitatetransistor formation. The dummy gate is replaced, usually by ahigh-k/metal gate, after source/drain formation. In a FUSI technique, apoly gate is first formed in order to facilitate transistor formation.The entire portion of the poly gate is then converted to silicide (e.g.,after source/drain formation).

BRIEF SUMMARY

In one exemplary embodiment of the invention, a semiconductor devicecomprising: a substrate; a borderless contact comprised of a metal; agate structure on the substrate; a first spacer disposed between thegate structure and the borderless contact and comprised of a firstspacer material; an interlevel dielectric that at least partiallyoverlies the gate structure; and a second spacer disposed between atleast a portion of the gate structure and the interlevel dielectric andcomprised of a second spacer material that is different from the firstspacer material.

In another exemplary embodiment of the invention, a method (e.g., tofabricate a semiconductor device having a borderless contact)comprising: forming a first gate structure on a substrate; depositing aninterlevel dielectric over the first gate structure; planarizing theinterlevel dielectric to expose a top surface of the first gatestructure; removing at least a portion of the first gate structure;forming a second gate structure in place of the first gate structure;forming a contact area for the borderless contact by removing a portionof the interlevel dielectric; and forming the borderless contact byfilling the contact area with a material comprised of a metal.

In a further exemplary embodiment of the invention, a semiconductordevice comprising: a substrate; and a gate structure on the substrate,the gate structure comprising a layer of semiconductor materialoverlying the substrate, a layer comprised of a metal overlying thelayer of semiconductor material, a layer comprised of polycrystallinesilicon overlying the layer comprised of a metal, a layer of silicideoverlying the layer comprised of polycrystalline silicon and a cap layeroverlying the layer of silicide.

In another exemplary embodiment of the invention, a semiconductor devicecomprising: a substrate; a gate structure on the substrate, the gatestructure comprising a metal gate core that is adjacent to a layer ofdielectric material on at least two surfaces of the metal gate core; anda cap layer overlying the layer of dielectric material and the metalgate core.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing and other aspects of embodiments of this invention aremade more evident in the following Detailed Description, when read inconjunction with the attached Drawing Figures, wherein:

FIG. 1 shows an exemplary, conventional multi-FET structure;

FIGS. 2-4 illustrate a conventional technique for forming a borderlesscontact in the multi-FET structure of FIG. 1;

FIGS. 5-10 show a first technique for forming a borderless contact in asemiconductor device in accordance with a first exemplary embodiment ofthe invention;

FIGS. 11-19 illustrate a second technique for forming a borderlesscontact in a semiconductor device in accordance with a second exemplaryembodiment of the invention;

FIGS. 20-26 depict a third technique for forming a borderless contact ina semiconductor device in accordance with a third exemplary embodimentof the invention;

FIGS. 27-31 show a fourth technique for forming a borderless contact ina semiconductor device in accordance with a fourth exemplary embodimentof the invention;

FIG. 32 depicts a flowchart illustrating one non-limiting example of amethod for practicing the exemplary embodiments of this invention;

FIG. 33 shows a flowchart illustrating another non-limiting example of amethod for practicing the exemplary embodiments of this invention;

FIG. 34 depicts a flowchart illustrating another non-limiting example ofa method for practicing the exemplary embodiments of this invention;

FIG. 35 shows a flowchart illustrating another non-limiting example of amethod for practicing the exemplary embodiments of this invention; and

FIG. 36 depicts a flowchart illustrating another non-limiting example ofa method for practicing the exemplary embodiments of this invention.

DETAILED DESCRIPTION 1. Further Considerations

FIG. 1 shows an exemplary, conventional multi-FET structure 10. Thestructure 10 includes a number of components or regions that areoverlying or embedded in a substrate (SUB) 12. There are STI regions 14and source/drain regions (S/D) 16. The SID 16 lies below portions of thegates 18. Each gate includes a number of layers (not labeled), such as:a dielectric layer (e.g., silicon oxide) overlying the substrate, a polylayer overlying the dielectric layer and a cap layer (e.g., nitride)overlying the poly. Surrounding each gate 18 are spacers (SPA) 20. TheSPA 20 and the nitride cap protect the other layers of the gate 18 fromundesired contacts and shorts. To reduce resistance, there may be alayer of silicide (SIL) 22 over the S/D 16.

FIGS. 2-4 illustrate a conventional technique for forming a borderlesscontact in the multi-FET structure of FIG. 1. As shown in FIG. 2, aninterlevel dielectric (ILD) 24 (e.g., an oxide) is deposited over thestructure 10. In FIG. 3, the contact is formed by patterning and RIE. Toform the borderless contact, the etched region is filled with a metal atthe CA 26, as depicted in FIG. 4.

In some cases, conventional techniques may result in a damaged spacer,for example, due to source/drain ion implantation, CA RIE or cleaning.Such a damaged spacer can cause electrical shorts between gate and CAcontacts, for example. Furthermore, thick spacers for the silicideformation and a tight pitch may result in a small CA space, leading to amore difficult CA fill. In addition, the nitride spacer has a highparasitic capacitance, inhibiting operation of the final structure.

As noted above, device scaling results in a small space for forming theborderless contact. Pitch scaling means there is a narrower space forthe CA and a bordered contact will not work. For example, consider a 22nm node having a pitch of 80 nm, a gate length of about 25 nm and aspacer thickness of about 18 nm per side. This leaves about 19 nm ofspace for the CA (80−25−2×18=19) which is too small for a borderedcontact. Furthermore, and also as noted above, conventional borderlesscontact techniques have various problems. Therefore, further techniquesare needed that improve upon conventional borderless contact techniques.

2. Various Exemplary Embodiments of the Invention

The exemplary embodiments of the invention provide a number ofimprovements over conventional borderless contacts and conventionalborderless contact techniques. Some of the exemplary embodiments seek toaddress and improve upon the above-noted shortcomings in prior artsystems.

A first exemplary embodiment of the invention provides for replacementof the spacers after the contact via etch. As a non-limiting example,the replacement spacers may be low-k spacers to reduce the parasiticcapacitance. The first exemplary embodiment also provides for formationof a second set of spacers above the cap of the gate (e.g., above thenitride cap and adjacent to the ILD). This second set of spacers mayalso be low-k spacers.

Various further exemplary embodiments of the invention describe how atleast a portion of the gate is removed after deposition andplanarization of the ILD. A second exemplary embodiment applies aborderless contact technique to a gate-first metal/poly/silicide gatestack. A cap layer (e.g., a nitride cap) is removed in order to enablethe formation of silicide on the gate structure (e.g., overlying a polylayer). Another cap layer (e.g., a nitride cap) is then formed (e.g.,overlying the silicide layer) by deposition and planarization.

A third exemplary embodiment describes a borderless contact techniquethat is utilized with a gate-last metal gate. A dummy gate is formedand, after deposition and planarization of the ILD, removed. Areplacement gate structure is then formed. As a non-limiting example,the replacement gate structure may comprise a layer of high-k dielectricthat surrounds (e.g., surrounds or encompasses on all sides except for asurface that is substantially coplanar with a top surface of thestructure) a metal gate. A cap layer (e.g., a nitride cap) issubsequently formed by deposition and planarization.

A fourth exemplary embodiment provides for a borderless contacttechnique that is utilized with a FUSI gate. After deposition andplanarization of the ILD, the cap layer (e.g., a nitride cap) is removed(e.g., using a RIE). The FUSI gate is then formed and another cap layer(e.g., a nitride cap) is formed (e.g., by deposition and planarization).

The exemplary embodiments of the invention and the various features andadvantageous details thereof will be explained more fully with referenceto the non-limiting exemplary embodiments that are illustrated in theaccompanying drawings and detailed in the following description. Itshould be noted that the features illustrated in the drawings are notnecessarily drawn to scale. Descriptions of well-known components andprocessing techniques (e.g., as known to one of ordinary skill in theart) are omitted so as to avoid unnecessarily obscuring the exemplaryembodiments of the invention. The examples used herein are intendedmerely to facilitate an understanding of ways in which the exemplaryembodiments of the invention may be practiced and to further enablethose of ordinary skill in the art to practice the exemplary embodimentsof the invention. Accordingly, the examples described herein should notbe construed as limiting the scope of the exemplary embodiments of theinvention.

As utilized herein, the following terms should be accorded the specifieddefinitions and/or meanings. It is believed that these definitions andmeanings are in accord with the understanding of one of ordinary skillin the art. “High-k,” such as a high-k dielectric, refers to a material(e.g., a dielectric) that has a relatively high dielectric constant,such as a dielectric constant greater than 7 (the dielectric constant ofsilicon nitride), for example. “Low-k,” such as a low-k dielectric,refers to a material (e.g., a dielectric) that has a relatively lowdielectric constant, such as a dielectric constant less than 3.9 (thedielectric constant of silicon oxide), for example. “Poly” refers to atleast one of polycrystalline silicon, polycrystalline germanium andpolycrystalline silicon germanium.

A. First Exemplary Embodiment

In the first exemplary embodiment, a plurality of FETs, each having agate stack comprised of a plurality of layers, are formed in accordancewith conventional processes (e.g., provision of a substrate, formationof isolation such as STIs, deposition of layers, patterning of thelayers into gate stacks using photolithography and etching, formation ofoxide and/or nitride spacers around the gate stacks (e.g., viadeposition and etching or via oxide growth), ion implantation for thesource/drain regions). As a non-limiting example, the plurality of FETsmay be similar to those shown in FIG. 1. For example, the gate structuremay comprise: a dielectric layer (e.g., silicon oxide, silicon nitride,silicon oxynitride, a high-k dielectric material, or any suitablecombination of such materials.) overlying the substrate, a poly layeroverlying the dielectric layer and a cap layer (e.g., nitride) overlyingthe poly. Surrounding each gate are spacers. As non-limiting examples,the nitride cap may be formed using a LPCVD process (e.g., a LPCVDnitride) and the spacers may be formed using a PECVD process (e.g., aPECVD nitride). As a further non-limiting example, there may be aplurality of spacers (e.g., an inner oxide spacer and an outer nitridespacer). Silicide may be formed at the source/drain regions.

An ILD 124 (e.g., an oxide) is deposited, resulting in the structureshown in FIG. 5. The contact via is formed, as illustrated in FIG. 6, bypatterning and etching (e.g., RIB). These processes may damage thespacers around the gate (e.g., the outer nitride spacers).

In accordance with the first exemplary embodiment, and as depicted inFIG. 7, the (possibly damaged) spacers are removed prior to filling thecontact with metal (e.g., a metal-containing material). While FIG. 7shows the removal of only the outer spacers (e.g., the outer nitridespacers), in other exemplary embodiments the inner spacers (e.g., theinner oxide spacers) are also removed.

As non-limiting examples, described below are several methods forremoving damaged PECVD nitride spacers. A selective etch (e.g., a wetetch process with an etch solution containing hydrofluoric/ethyleneglycol (HF/EG) or hot phosphoric acid) or a dry etch (e.g., a chemicaldownstream etch process) can be used to remove the PECVD nitrideselective to the LPCVD nitride (of the nitride cap) and the ILD. As afurther non-limiting example, an etch selectivity greater than 5:1 isachievable. Alternatively, a material other than nitride can be used asthe gate cap layer (e.g., silicon carbon). As a further alternative, anon-selective nitride etch may be performed. In this case, one can relyon a thickness difference between the nitride spacer and the nitridegate cap to ensure preservation of the nitride gate cap. For example,the nitride spacer may be about 200 A (about 200 angstroms) thick andthe nitride gate cap may be about 400 A thick. Therefore, a 250 Anitride etch, even without selectivity, will completely remove thenitride spacer while leaving a nitride gate cap of about 150 Athickness.

After removal of the spacers, new replacement spacers 128 are formed asshown in FIG. 8. The new replacement spacers 128 can be formed by anysuitable technique, such as a film deposition process followed by a RIEprocess, for example. The replacement spacers 128 may comprise anysuitable insulating material including, but not limited to: siliconoxide, silicon nitride, silicon oxynitride, silicon carbide, a low-kmaterial or any suitable combination of such materials. As anon-limiting example, the replacement spacers 128 may comprise a low-kmaterial. Exemplary low-k dielectric materials include organosilicateglass (OSG) and SiLK™. Furthermore, the replacement spacers 128 may bethinner than the original spacers. Formation of these new replacementspacers 128 cures potential defects in the original spacers, such as apinhole, for example.

In conjunction with forming the replacement spacers 128, an additionalset of spacers 130 may be formed. These additional spacers 130 areformed on the sidewalls of the ILD that is located above the gatestructures, as illustrated in FIG. 9. To form the borderless contact,the etched region is filled with conductive material (e.g., a metal, ametal-containing material, a material comprising a metal) at the CA 126,as depicted in FIG. 10.

Forming the new replacement spacers 128 after the contact via etchprovides improved isolation between the contact and the gate. Thisexemplary technique also enables the usage of narrow spacers tofacilitate the CA fill (i.e., a wide CA space) and the usage of low-kspacers to reduce parasitic capacitance. In addition, this exemplarytechnique can provide asymmetric spacers, for example, whereby theoriginal (e.g., nitride) spacers covered by the ILD have a firstthickness and the new replacement (e.g., low-k) spacers have a secondthickness (e.g., that is thinner than the first thickness).

B. Second Exemplary Embodiment

In the second exemplary embodiment, a plurality of FETs (e.g., amulti-FET structure 210), each having a gate stack comprised of aplurality of layers, are formed in accordance with conventionalprocesses (e.g., provision of a substrate, formation of STIs, depositionof layers, patterning of the layers into gate stacks usingphotolithography and etching, formation of oxide or nitride spacersaround the gate stacks (e.g., via deposition and etching or via oxidegrowth), ion implantation for the source/drain regions).

FIG. 11 shows an exemplary multi-FET structure 210. The structure 210includes a number of components or regions that are overlying orembedded in a substrate (SUB) 212. There are STI regions 214 andsource/drain regions (S/D) 216. The S/D 216 lie below portions of thegates 218. Each gate includes a number of layers as described furtherbelow. Surrounding each gate 218 are spacers (SPA) 220. The SPA 220 andthe cap protect the other layers of the gate 218 from undesired contactsand shorts. To reduce resistance, there may be a layer of silicide (SIL)222 over the SID 216.

FIG. 12 shows an exemplary gate stack 218 for the multi-FET structure210 of FIG. 11. The exemplary gate stack 218 includes: a high-kdielectric layer (HIGH-K) 230 overlying the SUB 212, a metal layer (MET)232 overlying the HIGH-K 230, a poly layer (POLY) 234 overlying theHIGH-K 230 and a cap layer (CAP) 236 overlying the POLY 234. As anon-limiting example, the CAP 236 may comprise a nitride cap or anitride cap layer. For completeness, the SPA 220 surrounding the gate218 are also shown in FIG. 12. As a non-limiting example, there may be aplurality of spacers (e.g., an inner oxide spacer and an outer nitridespacer).

An interlayer dielectric (ILD) 224, such as an oxide with a nitrideliner, for example, is deposited and planarized, resulting in thestructure shown in FIG. 13. Subsequently, and as shown in FIG. 14, theCAPs 236 on each gate (or at least one gate) are removed. As depicted inFIG. 15, a layer of silicide (SIL2) 238 is formed on each gate (i.e.,each gate whose cap was removed). As illustrated in FIG. 16, a new cap(CAP2) 240 is fowled on each gate (i.e., each gate that received a layerof SIL2 238). The CAP2 240 may be formed by deposition andplanarization. Furthermore, as a non-limiting example the CAP2 240 maycomprise a nitride cap. Optionally, and as shown in FIG. 17, a secondlayer of ILD (ILD2) 242 is deposited and planarized. As shown in FIG.18, a contact mask (MASK) 244 and a contact RIE are used to remove theILD material from between the gates 218, thus forming the space for theborderless contact. The MASK 244 is removed and the contact area (CA)226 is formed, as illustrated in FIG. 19, by filling the contact withconductive material, such as a metal, a metal-containing material or amaterial comprising a metal, as non-limiting examples. In some exemplaryembodiments, the opening on the MASK 244 is wider than the space betweenthe neighboring gates.

The exemplary technique illustrated by FIGS. 11-19 depict the formationof a borderless contact (e.g., in a MOSFET) with a gate-first metal gatecapped by a low resistance poly/silicide layer 238. The final structureof the gate stack includes a high-k gate dielectric (HIGH-K 230)overlying the substrate (SUB 212), a metal layer (MET 232) overlying thehigh-k gate dielectric (HIGH-K 230), a poly layer (POLY 234) overlyingthe metal layer (MET 232), a silicide layer (SIL2 238) overlying thepoly layer (POLY 234) and an insulating cap layer (CAP2 240) overlyingthe silicide layer (SIL2 238). The borderless contact is isolated fromthe gate by a spacer(s) (SPA 220) and the insulating cap layer (CAP2240).

C. Third Exemplary Embodiment

In the third exemplary embodiment, a plurality of FETs (e.g., amulti-FET structure 310 as shown in FIG. 20 or a multi-FET structure 10as shown in FIG. 1), each having a gate stack comprised of a pluralityof layers, are formed in accordance with conventional processes (e.g.,provision of a substrate, formation of STIs, deposition of layers,patterning of the layers into gate stacks using photolithography andetching, formation of oxide or nitride spacers around the gate stacks(e.g., via deposition and etching or via oxide growth), ion implantationfor the source/drain regions). As a non-limiting example, the pluralityof FETs may be similar to those shown in FIG. 1. For example, the gatestructure may comprise: a dielectric layer (e.g., silicon oxide)overlying the substrate, a poly layer overlying the dielectric layer anda cap layer (e.g., nitride) overlying the poly. Surrounding each gateare spacers. As a further non-limiting example, there may be a pluralityof spacers (e.g., an inner oxide spacer and an outer nitride spacer).Silicide may be formed at the source/drain regions.

In comparison to the conventional FETs of FIG. 1 and the first andsecond exemplary embodiments, the initial FETs of the third exemplaryembodiment comprise dummy gates. That is, since the third exemplaryembodiment utilizes a gate-last technique, the initial gates are dummygates (e.g., placeholders) that will be replaced at a later time (e.g.,after deposition of the ILD). While the initial gates are dummy gates,they may be formed using similar (e.g., conventional) techniques.

As shown in FIG. 20, an interlayer dielectric (ILD) 324 is deposited andplanarized. As a non-limiting example, the ILD 324 may comprise an oxidewith a nitride liner. Thereafter, and as illustrated in FIG. 21, thedummy gates are removed, for example, via selective etching or otherconventional techniques. As depicted in FIG. 22, a high-k dielectric(HKD) 330 is deposited over the structure (e.g., the entire structure,including the ILD 324). Subsequently, and as shown in FIG. 23, a metalgate (MG) 332 is deposited, planarized and recessed. The MG 332 forms ametal gate core and is surrounded (e.g., adjacent) on at least twosides/surfaces by the dielectric (e.g., the HKD 330 is adjacent to atleast sidewall surfaces and a bottom surface of the MG 332; the HKD 330may not be adjacent to a top surface of the MG 332). As an optionallystep, the exposed portions of the HKD 330 can be removed, resulting inthe structure shown in FIG. 24.

As illustrated in FIG. 25, a new cap (CAP2) 340 is formed on each gate(i.e., each gate for which a gate stack was formed in place of theremoved dummy gate). The CAP2 340 may be formed by deposition andplanarization. Furthermore, as a non-limiting example the CAP2 340 maycomprise a nitride cap. Optionally, and as shown in FIG. 26, a secondlayer of ILD (ILD2) 342 is deposited and planarized. A contact mask anda contact RIE are used to remove the ILD material from between thegates, thus forming the space for the borderless contact. The mask isremoved and the contact area (CA) 326 is formed, as illustrated in FIG.26, by filling the contact with conductive material, such as a metal, ametal-containing material or a material comprising a metal, asnon-limiting examples.

The exemplary technique illustrated by FIGS. 20-26 depict the formationof a borderless contact (e.g., in a MOSFET) with a gate-last gate (e.g.,a metal gate). As a non-limiting example, the final structure of thegate stack may include a metal gate core (MG 332) that is surrounded(e.g., adjacent) on at least two sides/surfaces by a dielectric (e.g., ahigh-k dielectric such as HKD 330, which is adjacent to at leastsidewall surfaces and a bottom surface of the MG 332). The dielectricmay not be adjacent to a top surface of the metal gate core. Theborderless contact is isolated from the gate by a spacer(s) and theinsulating cap layer (CAP2 340).

D. Fourth Exemplary Embodiment

In the fourth exemplary embodiment, a plurality of FETs (e.g., amulti-FET structure 410 as shown in FIG. 27 or a multi-FET structure 10as shown in FIG. 1), each having a gate stack comprised of a pluralityof layers, are formed in accordance with conventional processes (e.g.,provision of a substrate, formation of STIs, deposition of layers,patterning of the layers into gate stacks using photolithography andetching, formation of oxide or nitride spacers around the gate stacks(e.g., via deposition and etching or via oxide growth), ion implantationfor the source/drain regions). As a non-limiting example, the pluralityof FETs may be similar to those shown in FIG. 1. For example, the gatestructure may comprise: a dielectric layer (e.g., silicon oxide)overlying the substrate, a poly layer overlying the dielectric layer anda cap layer (e.g., nitride) overlying the poly. Surrounding each gateare spacers. As a further non-limiting example, there may be a pluralityof spacers (e.g., an inner oxide spacer and an outer nitride spacer).Silicide may be formed at the source/drain regions.

As shown in FIG. 27, an interlayer dielectric (ILD) 424 is deposited andplanarized. As a non-limiting example, the ILD 424 may comprise an oxidewith a nitride liner. Thereafter, and as illustrated in FIG. 28, the caplayer (e.g., the nitride cap) on each gate stack is removed, resultingin an exposed gate stack 430. As a non-limiting example, the exposedgate stacks 430 each may comprise a layer of gate dielectric (e.g.,high-k dielectric material) overlying the substrate and a layer ofpolysilicon overlying the layer of gate dielectric. Also as anon-limiting example, the cap layer(s) may be removed using a RIE.

After the cap layer is removed for each gate in question, a FUSI gate(FG) 432 is formed for each gate stack, as illustrated in FIG. 29. TheFG 432 may be formed using processes and techniques that are known inthe art. As a non-limiting example, the FG 432 may be formed using thetechniques disclosed by Tan et al. in “Formation of a Thermally StableNiSi FUSI Gate Electrode by a Novel Integration Process,” Mater. Res.Soc. Symp. Proc., Vol. 958 (0958-L06-08), 2007.

As depicted in FIG. 30, a new cap (CAP2) 440 is formed on each gate(i.e., each gate for which a FG 432 was formed). The CAP2 440 may beformed by deposition and planarization. Furthermore, as a non-limitingexample the CAP2 340 may comprise a nitride cap. Optionally, and asshown in FIG. 31, a second layer of ILD (ILD2) 442 is deposited andplanarized. A contact mask and a contact RIB are used to remove the ILDmaterial from between the gates, thus forming the space for theborderless contact. The mask is removed and the contact area (CA) 426 isformed, as illustrated in FIG. 31, by filling the contact withconductive material, such as a metal, a metal-containing material or amaterial comprising a metal, as non-limiting examples.

The exemplary technique illustrated by FIGS. 27-31 depict the formationof a borderless contact (e.g., in a MOSFET) with a FUSI gate (e.g., FG432). As a non-limiting example, the final structure of the gate stackincludes a FUSI gate structure (e.g., FG 432) that has a replacement ornew cap layer (e.g., a nitride cap such as CAP2 440). The borderlesscontact is isolated from the gate by a spacer(s) and the insulating caplayer (CAP2 440).

3. Further Exemplary Embodiments of the Invention

Below are further descriptions of various non-limiting, exemplaryembodiments of the invention. The below-described exemplary embodimentsare numbered separately for clarity purposes. This numbering should notbe construed as entirely separating the various exemplary embodimentssince aspects of one or more exemplary embodiments may be practiced inconjunction with one or more other aspects or exemplary embodiments.

(1A) In one exemplary embodiment, and as shown in FIG. 32, a method(e.g., to fabricate a semiconductor device having a borderless contact)comprising: forming a gate structure on a substrate (501); forming atleast one first spacer around the gate structure (502); depositing aninterlevel dielectric over the gate structure and the at least one firstspacer (503); forming a contact area for the borderless contact byremoving a portion of the interlevel dielectric, wherein removal of theportion of the interlevel dielectric exposes at least a portion of theat least one first spacer (504); removing the exposed portion of the atleast one first spacer (505); forming at least one second spacer aroundthe gate structure (506); and forming the borderless contact by fillingthe contact area with a material comprised of a metal (507).

A method as above, further comprising: forming at least one third spacerabove the gate structure and adjacent to the interlevel dielectric. Amethod as in any above, where forming at least one first spacer aroundthe gate structure comprises forming the first spacer around the gatestructure and forming a fourth spacer around the gate structure, wherethe fourth spacer comprises an inner spacer and the first spacercomprises an outer spacer. A method as in any above, where removing theexposed portion of the at least one first spacer does not result inremoval of a portion of the fourth spacer. A method as in any above,where the at least one first spacer comprises a nitride and the at leastone second spacer comprises a low-k dielectric material. A method as inany above, further comprising one or more additional aspects of theexemplary embodiments of the invention as described herein.

(1B) In a further exemplary embodiment, a semiconductor devicecomprising: a substrate; a borderless contact comprised of a metal; agate structure on the substrate; a first spacer disposed between thegate structure and the borderless contact and comprised of a firstspacer material; an interlevel dielectric that at least partiallyoverlies the gate structure; and a second spacer disposed between atleast a portion of the gate structure and the interlevel dielectric andcomprised of a second spacer material that is different from the firstspacer material.

The semiconductor device as above, further comprising a third spacerdisposed on the gate structure and between the interlevel dielectric andthe borderless contact. The semiconductor device as in any above,further comprising a fourth spacer disposed between the gate structureand the first spacer, where the fourth spacer comprises an inner spacerand the first spacer comprises an outer spacer. The semiconductor deviceas in any above, where the first spacer comprises a nitride and thesecond spacer comprises a low-k dielectric material. The semiconductordevice as in any above, where the semiconductor device comprises a metaloxide semiconductor field effect transistor. The semiconductor device asin any above, further comprising one or more additional aspects of theexemplary embodiments of the invention as described herein.

(2) In another exemplary embodiment, and as shown in FIG. 33, a method(e.g., to fabricate a semiconductor device having a borderless contact)comprising: forming a first gate structure on a substrate (601);depositing an interlevel dielectric over the first gate structure (602);planarizing the interlevel dielectric to expose a top surface of thefirst gate structure (603); removing at least a portion of the firstgate structure (604); forming a second gate structure in place of thefirst gate structure (605); forming a contact area for the borderlesscontact by removing a portion of the interlevel dielectric (606); andforming the borderless contact by filling the contact area with amaterial comprised of a metal (607).

A method as above, where the first gate structure comprises a dummy gatestructure and where removing the at least a portion of the first gatestructure comprises removing substantially all of the dummy gatestructure. A method as in any above, where the removed portion of thefirst gate structure comprises a first cap layer of the first gatestructure. A method as in any above, where forming the second gatestructure comprises forming a layer of silicide and forming a second caplayer. A method as in any above, where forming the second gate structurecomprises forming a fully silicided gate structure. A method as in anyabove, where the first gate structure comprises a layer of dielectricmaterial overlying the substrate, a layer comprised of polycrystallinesilicon overlying the layer dielectric material and the first cap layeroverlying the layer comprised of polycrystalline silicon. A method as inany above, where forming the second gate structure comprises forming asecond cap layer overlying the fully silicided gate. A method as in anyabove, where forming the contact area for the borderless contactcomprises depositing a second layer of interlevel dielectric andplanarizing the second layer of interlevel dielectric. A method as inany above, where the interlevel dielectric comprises an oxide with anitride liner. A method as in any above, where the semiconductor devicecomprises a metal oxide semiconductor field effect transistor. A methodas in any above, further comprising one or more additional aspects ofthe exemplary embodiments of the invention as described herein.

(3A) In another exemplary embodiment, and as shown in FIG. 34, a method(e.g., to fabricate a semiconductor device having a borderless contact)comprising: forming a gate structure (GS) on a substrate (SUB), the gatestructure comprising a layer of semiconductor material overlying thesubstrate, a layer comprised of a metal overlying the layer ofsemiconductor material, a layer comprised of polycrystalline siliconoverlying the layer comprised of a metal and a first cap layer (CAP1)overlying the layer comprised of polycrystalline silicon (701);depositing an interlevel dielectric (ILD) over the gate structure (702);planarizing the interlevel dielectric to expose a top surface of thegate structure (703); removing the first cap layer of the gate structure(704); forming a layer of silicide in the gate structure, the layer ofsilicide overlying the layer comprised of polycrystalline silicon (705);forming a second cap layer (CAP2) in the gate structure, the second caplayer overlying the layer of silicide (706); forming a contact area (CA)for the borderless contact by removing a portion of the interleveldielectric (707); and forming the borderless contact by filling thecontact area with a material comprised of a metal (708).

A method as above, where the interlevel dielectric comprises an oxidewith a nitride liner. A method as in any above, where the second caplayer comprises a nitride. A method as in any above, where theborderless contact is disposed between the gate structure and anothergate structure. A method as in any above, where forming the contact areafor the borderless contact comprises using a contact mask and a contactreactive ion etch to remove the portion of the interlevel dielectric,where an opening on the contact mask is wider than a space between thegate structure and the other gate structure. A method as in any above,further comprising one or more additional aspects of the exemplaryembodiments of the invention as described herein.

(3B) In a further exemplary embodiment, a semiconductor devicecomprising: a substrate; and a gate structure on the substrate, the gatestructure comprising a layer of semiconductor material overlying thesubstrate, a layer comprised of a metal overlying the layer ofsemiconductor material, a layer comprised of polycrystalline siliconoverlying the layer comprised of a metal, a layer of silicide overlyingthe layer comprised of polycrystalline silicon and a cap layer overlyingthe layer of silicide.

The semiconductor device as above, where the cap layer comprises anitride. The semiconductor device as in any above, further comprising:an interlevel dielectric that at least partially overlies the gatestructure; and a borderless contact comprised of a metal. Thesemiconductor device as in any above, where the interlevel dielectriccomprises an oxide with a nitride liner. The semiconductor device as inany above, where the semiconductor device comprises a metal oxidesemiconductor field effect transistor. The semiconductor device as inany above, further comprising one or more additional aspects of theexemplary embodiments of the invention as described herein.

(4A) In another exemplary embodiment, and as shown in FIG. 35, a method(e.g., to fabricate a semiconductor device having a borderless contact)comprising: forming a dummy gate structure on a substrate (801);depositing an interlevel dielectric over the dummy gate structure (802);planarizing the interlevel dielectric to expose a top surface of thedummy gate structure (803); removing the dummy gate structure (804);forming a second gate structure in place of the dummy gate structure(805); forming a contact area for the borderless contact by removing aportion of the interlevel dielectric (806); and forming the borderlesscontact by filling the contact area with a material comprised of a metal(807).

A method as above, where forming the second gate structure in place ofthe dummy gate structure comprises: depositing a layer of dielectricmaterial; depositing a material comprised of a metal; planarizing andrecessing the material comprised of a metal to form a metal gate core inthe second gate structure that is adjacent to the layer of dielectricmaterial on at least two surfaces of the metal gate core; and forming acap layer overlying the layer of dielectric material and the metal gatecore. A method as in any above, where a top surface of the metal gatecore is not covered by the layer of dielectric material. A method as inany above, where the at least two surfaces comprise at least onesidewall surface and a bottom surface. A method as in any above, wherethe at least two surfaces does not comprise a top surface of the metalgate core. A method as in any above, further comprising one or moreadditional aspects of the exemplary embodiments of the invention asdescribed herein.

(4B) In a further exemplary embodiment, a semiconductor devicecomprising: a substrate; a gate structure on the substrate, the gatestructure comprising a metal gate core that is adjacent to a layer ofdielectric material on at least two surfaces of the metal gate core; anda cap layer overlying the layer of dielectric material and the metalgate core.

The semiconductor device as in any above, where a top surface of themetal gate core is not covered by the layer of dielectric material. Thesemiconductor device as in any above, where the at least two surfacescomprise at least one sidewall surface and a bottom surface.

The semiconductor device as in any above, where the at least twosurfaces do not comprise a top surface of the metal gate core. Thesemiconductor device as in any above, further comprising: an interleveldielectric that at least partially overlies the gate structure; and aborderless contact comprised of a metal. The semiconductor device as inany above, further comprising one or more additional aspects of theexemplary embodiments of the invention as described herein.

(5) In another exemplary embodiment, and as shown in FIG. 36, a method(e.g., to fabricate a semiconductor device having a borderless contact)comprising: forming a gate structure on a substrate, the gate structurecomprising a layer of dielectric material overlying the substrate, alayer comprised of polycrystalline silicon overlying the layerdielectric material and a first cap layer overlying the layer comprisedof polycrystalline silicon (901); depositing an interlevel dielectricover the gate structure (902); planarizing the interlevel dielectric toexpose a top surface of the gate structure (903); removing the first caplayer of the gate structure (904); forming a fully silicided gate inplace of the gate structure (905); forming a second cap layer overlyingthe fully silicided gate (906); forming a contact area for theborderless contact by removing a portion of the interlevel dielectric(907); and forming the borderless contact by filling the contact areawith a material comprised of a metal (908).

A method as in any above, further comprising one or more additionalaspects of the exemplary embodiments of the invention as describedherein.

The blocks shown in FIGS. 32-36 further may be considered to correspondto one or more functions and/or operations that are performed inconjunction with one or more components, circuits, chips, apparatus,processors, computer programs and/or function blocks. Any and/or all ofthe above may be implemented in any practicable solution or arrangementthat enables operation in accordance with the exemplary embodiments ofthe invention as described herein.

In addition, the arrangement of the blocks depicted in FIGS. 32-36should be considered merely exemplary and non-limiting. It should beappreciated that the blocks shown in FIGS. 32-36 may correspond to oneor more functions and/or operations that may be performed in any order(e.g., any suitable, practicable and/or feasible order) and/orconcurrently (e.g., as suitable, practicable and/or feasible) so as toimplement one or more of the exemplary embodiments of the invention. Inaddition, one or more additional functions, operations and/or steps maybe utilized in conjunction with those shown in FIGS. 32-36 so as toimplement one or more further exemplary embodiments of the invention.

That is, the exemplary embodiments of the invention shown in FIGS. 32-36may be utilized, implemented or practiced in conjunction with one ormore further aspects in any combination (e.g., any combination that issuitable, practicable and/or feasible) and are not limited only to thesteps, blocks, operations and/or functions shown in FIGS. 32-36.

The flowchart and block diagrams in FIGS. 32-36 illustrate thearchitecture, functionality, and operation of possible exemplaryimplementations of systems, methods and products according to variousexemplary embodiments of the invention. In this regard, each block inthe flowchart or block diagrams may represent a module, segment orportion of code, which comprises one or more executable instructions forimplementing the specified (logical) function(s). It should also benoted that, in some alternative exemplary implementations, the functionsnoted in the block may occur out of the order noted in the figures. Forexample, two blocks shown in succession may, in fact, be executedsubstantially concurrently, or the blocks may sometimes be executed inthe reverse order, depending upon the functionality involved. It willalso be noted that each block of the block diagrams and/or flowchartillustration, and combinations of blocks in the block diagrams and/orflowchart illustration, can be implemented by special purposehardware-based systems that perform the specified functions or acts, orcombinations of special purpose hardware and computer instructions.

The exemplary methods and techniques described herein may be used in thefabrication of integrated circuit chips. The resulting integratedcircuit chips can be distributed by the fabricator in raw wafer form(i.e., as a single wafer that has multiple unpackaged chips), as a baredie, or in a packaged form. In the latter case, the chip is mounted in asingle chip package (e.g., a plastic carrier, with leads that areaffixed to a motherboard or other higher level carrier) or in amultichip package (e.g., a ceramic carrier that has either or bothsurface interconnections or buried interconnections). The chip is thenintegrated with other chips, discrete circuit elements and/or othersignal processing devices as part of either (a) an intermediate product,such as a motherboard, or (b) an end product. The end product can be anyproduct that includes integrated circuit chips, ranging from toys andother low-end applications to advanced computer products having numerouscomponents, such as a display, a keyboard or other input device and/or acentral processor, as non-limiting examples.

The terminology used herein is for the purpose of describing particularexemplary embodiments only and is not intended to be limiting of theexemplary embodiments of the invention. As used herein, the singularforms “a”, “an” and “the” are intended to include the plural forms aswell, unless the context clearly indicates otherwise. It will be furtherunderstood that the terms “comprises” and/or “comprising,” when used inthis specification, specify the presence of stated features, integers,steps, operations, elements and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components and/or groups thereof.

Unless described otherwise herein, “depositing” may include any nowknown or later developed techniques appropriate for the material to bedeposited, including, but not limited to: CVD, LPCVD, PECVD,semi-atmosphere CVD (SACVD), high density plasma CVD (HDPCVD), rapidthermal CVD (RTCVD), ultra-high vacuum CVD (UHVCVD), limited reactionprocessing CVD (LRPCVD), metalorganic CVD (MOCVD), sputteringdeposition, ion beam deposition, electron beam deposition, laserassisted deposition, thermal oxidation, thermal nitridation, spin-onmethods, physical vapor deposition (PVD), atomic level deposition (ALD),chemical oxidation, molecular beam epitaxy (MBE), plating orevaporation. Any references to “poly” or “poly silicon” should beunderstood to refer to polycrystalline silicon.

Any use of the terms “connected,” “coupled” or variants thereof shouldbe interpreted to indicate any such connection or coupling, direct orindirect, between the identified elements. As a non-limiting example,one or more intermediate elements may be present between the “coupled”elements. The connection or coupling between the identified elements maybe, as non-limiting examples, physical, electrical, magnetic, logical orany suitable combination thereof in accordance with the describedexemplary embodiments. As non-limiting examples, the connection orcoupling may comprise one or more printed electrical connections, wires,cables, mediums or any suitable combination thereof.

Generally, various exemplary embodiments of the invention can beimplemented in different mediums, such as software, hardware, logic,special purpose circuits or any combination thereof. As a non-limitingexample, some aspects may be implemented in software which may be run ona computing device, while other aspects may be implemented in hardware.

The foregoing description has provided by way of exemplary andnon-limiting examples a full and informative description of the bestmethod and apparatus presently contemplated by the inventors forcarrying out the invention. However, various modifications andadaptations may become apparent to those skilled in the relevant arts inview of the foregoing description, when read in conjunction with theaccompanying drawings and the appended claims. However, all such andsimilar modifications will still fall within the scope of the teachingsof the exemplary embodiments of the invention.

Furthermore, some of the features of the preferred embodiments of thisinvention could be used to advantage without the corresponding use ofother features. As such, the foregoing description should be consideredas merely illustrative of the principles of the invention, and not inlimitation thereof.

What is claimed is:
 1. A semiconductor device comprising: a substrate; agate structure on the substrate, the gate structure comprising a metalgate core, where at least two surfaces of the metal gate core aredirectly adjacent to, and in direct contact with, a same layer ofdielectric material, where the at least two surfaces comprise at leastone sidewall surface and a bottom surface; and a cap layer overlying thelayer of dielectric material and the metal gate core.
 2. Thesemiconductor device of claim 1, where a top surface of the metal gatecore is not covered by the layer of dielectric material.
 3. Thesemiconductor device of claim 1, where the at least two surfaces do notcomprise a top surface of the metal gate core.
 4. The semiconductordevice of claim 1, further comprising: an interlevel dielectric that atleast partially overlies the gate structure; and a borderless contactcomprised of a metal.